In recent years, a display apparatus comprising a liquid crystal panel as an image display part is widespread. Such a display apparatus is so configured that a backlight (lighting device) is placed at the back side of the liquid crystal panel and the light emitted from the backlight is modulated by and transmitted through the liquid crystal panel to display an image on the front surface of the liquid crystal panel.
As a backlight, an edge light type backlight is known. The edge light type backlight comprises a light guide plate and a light source that are housed inside a box-shaped backlight chassis (casing) that has an opening at its one side. The light guide plate is mounted on the bottom plate of the backlight chassis, and the light source is fixed to a side plate of the backlight chassis to face a side surface of the light guide plate. The light source employs a light emitting diode (LED) or the like. This backlight is used in the state where the light guide plate is placed to face a back surface of the liquid crystal panel. In the backlight as described above, the light emitted from the light source enters the light guide plate through the side surface thereof and progresses inside the light guide plate while being diffused to be emitted from one surface of the light guide plate to illuminate the liquid crystal panel.
In the backlight having the configuration described above, heat generated during the light emission of the light source expands the light guide plate, which make contact with the light source, causing defect such as damage to the light source.
In the backlight device described in Japanese Patent Application Laid-open No 2012-164507, a support member for positioning the light guide plate is provided inside the casing, and a notch into which the support member is fitted is formed at the optimal position with respect to the light guide plate, such as at a light incident surface facing the light source of the light guide plate or the central part of the left or right side surface of the light guide plate, to control the movement of the thermally expanded light guide plate by fitting the support member into the notch. The extension of the light guide plate toward the light source is thereby restrained even when the light guide plate thermally expands, so that the contact between the light guide plate and the light source can be avoided.